Posts tagged with django-cms

... or how to reuse your plugins inside sections with different design

Problem: Frequently on the websites I am developing I need to display same set of data in several different ways. For example if I have a news box that needs to appear in different sections of the website e.i. in sidebar, main content etc. Using Django CMS plugins make this quite easy.
For simplicity we will take the following case. An image/text tuple with two layout variations - image on left of text and image on right.

Same data but different layout. All you need to do is just to allow your users to change the plugin template according to their needs. If you don't have experience with Django CMS Plugins I advice you to check how to create custom Django CMS Plugins before you continue with solution.

Solution: First you will have to create a tuple holding your templates(and their human readable names) and add a field that will hold the chosen template to the plugin model.

Final words: Yep, this is all. Simple isn't it? It is amazing how sometimes such small things are so useful. If you are having bigger difference in the layout of your templates you will probably have to put a little more stuff in the context that some of your templates may not need but it is OK. Feel free to comment and if you are using this "trick" please add your use case - it will be interesting to see in how many different cases this works.

... or how to avoid duplicate content by keeping the current language in the URL

Preface: Earlier this year I posted about Django CMS 2.2 features that I want to see and one of the things mentioned there was that once you have chosen the language of the site there is no matter whether you will open "/my_page/" or "/en/my_page/" - it just shows the same content. The problem is that this can be considered both duplicate and inconsistent content.
Duplicate because you see the same content with and without the language code in the URL and inconsistent because for the same URL you can get different language versions i.e. different content.

Solution: This can be easy fixed by using a custom middleware that will redirect the URL that does not contain language code. In my case the middleware is stored in "middleware/URLMiddlewares.py"(the path is relative to my project root directory) and contains the following code.

Now a little explanation on what happens in this middleware.
Note: If you are not familiar with how middlewares work go and check Django Middlewares.
Back to the code. First we split the URL by '/' and take the second element(this is where our language code should be) and store in lang_path(8).
URLS_WITHOUT_LANGUAGE_REDIRECT is just a list of URLs that should not be redirected, if lang_path matches any of the URLs we return None i.e. the request is not changed(9-10). This is used for sections of the site that are not language specific for example media stuff.
Then we get language based on the request(11-13).
If lang_path is empty then the user has requested the home page and we redirect him to the correct language version of it(14-15).
If lang_path does not match any of the declared languages this mean that the language code is missing from the URL and the user is redirected to the correct language version of this page(16-17).
To make the middleware above to work you have to update your settings.py.
First add the middleware to your MIDDLEWARE_CLASSES - in my case the path is 'middleware.URLMiddlewares.CustomMultilingualURLMiddleware'.
Second add URLS_WITHOUT_LANGUAGE_REDIRECT list and place there the URLs that should not be redirected, example:

URLS_WITHOUT_LANGUAGE_REDIRECT=['css','js',]

Specialties: If the language code is not in the URL and there is no language cookie set your browser settings will be used to determine your preferred language. Unfortunately most of the users do not know about this option and it often stays set to its default value. If you want this setting to be ignored just add the following code after line 10 in the middleware above:

It removed the HTTP_ACCEPT_LANGUAGE header sent from the browser and Django uses the language set in its settings ad default.

URLS_WITHOUT_LANGUAGE_REDIRECT is extremely useful if you are developing using the built in dev server and serve the media files trough it. But once you put your website on production I strongly encourage you to serve these files directly by the web server instead of using Django static serve.

Final words: In Django 1.4 there will be big changes about multilingual URLs but till then you can use this code will improve your website SEO. Any ideas of improvement will be appreciated.

... how to make usable drop-downs with Django CMS pages

Problem: some times when you create custom applications or plugins for Django CMS you need a property that connects the current item to a page in the CMS. Nothing simple than this - you just add a ForeignKey in your model that points to the Page model and everything is (almost)fine. Example:

If you registered your model in Django admin or just add a model form to it you will see something like this:

Cool right? Not exactly. The problem is that these pages are in hierarchical structure and listing them in a flat list may be/is little confusing. So let's indent them accordingly to their level in the hierarchy.
Solution: The easies way to achieve this indentation is to overwrite the choices list of the ForeignKey field in the ModelForm __init__ method.

The magic lies between lines 7 and 11, on line 7 we create a list with one element the default empty option for the drop down. The need to use "__iter__().next()" comes from the fact that the choices attribute of the fields is django.forms.models.ModelChoiceIterator object which is iterable, but not indexable i.e. you can not just use self.fields['url'].choices[0].
After we had the empty choice now it is time to add the real ones, so we iterate over the queryset(8th line) that holds them and for each item we add a tuple to our choices list(10). The first item of the tuple is the page id - nothing special, but the second one... here the python magic comes. We multiple the minus sign('-') by the page level and join the result with the page title. The only thing left is to replace the field choices(line 12) and here is the result:

Final words: For me this is much more usable than the flat list. Of course you can modify the queryset to return only published pages or filter the results in other way and still use the identation code from above.
I'll be happy to hear your thoughts on this.

... or how to make user editable 404 page that stays in the pages tree of the CMS

Basics: Yes you need it! You need 404 page cause you never know what may happen to a link: bad link paste, obsolete or deleted article, someone just playing with your URLs etc. It is better for both you and your website visitors to have a beauty page that follows the website design instead of the webserver default one that usually contains server information which is possible security issue. With Django this is easy, just make a HTML template with file name 404.html, place it in you root template directory and voilà - you are ready. You will also automatically have a request_path variable defined in the context which caries the URL that was not found.

Problem: sometimes clients require to be able to edit their 404 pages. Or other times you need to use some custom context or you want to integrate plug-ins and be able to modify them easy trough the CMS administration. For example: you want do display your brand new awesome "Sitemap Plug-in" on this 404 page.

Solution: Django allows you to specify custom 404 handler view so you just need to define one, set it in urls.py and make it to render the wanted page:

# in urls.pyhandler404='site_utils.handler404'# in site_utils.pyfromcms.viewsimportdetailsdefhandler404(request):returndetails(request,'404-page-url')

Where '404-page-url' is the URL of the page you want to show for 404 errors. So everything seems fine and here is the pitfall. If you use it this way your web page will return "200 OK" instead of "404 Not Found". This could kill your SEO(except if you want your 404 page as first result for your website). So you just need to add a 404 header to the response:

Final words: Why are these HTTP status codes so important. The reason is that they tells the search engines and other auto crawling services what is the page status. Is it normal page, redirect, not found, error or something else. Providing incorrect status codes may/will have a negative effect on your website SEO so try to keep them correct, especially when it is easy to achieve as in the example above.

Note: If the code above is not working for you, please check Allan's solution in the comments

Preface: I have to admit that I was expecting a bigger interest in the "Post on request" topic but probably my blog is too young for this but I think I will try again(soon or not). The more important thing is that Jonas Obrist is the indisputable winner of this month "contest".

Features: One of the most useful features in the next Django CMS must be the ability to copy placeholder's content between different language version of one page. For example imagine that you have a home page with several placeholder each with several plugins/snippets inside(latest news, featured products etc.) when creating new language version of the page it is really annoying when you have to add this one by one.

One other feature requested by my colleague Miro is a little opposite of the one I want, he want to be able to add different page templates for each language version of the page. I also find this useful because sometimes your language version are not fully mirrored even on the same page.

Bugs: I am not sure that this is actually a bug but I think it is bad for SEO so I will mark it. If you have a multilingual website, once you have the language set in the cookie the same page is displayed no matter whether you have the language code in the URL. For example, "/en/news/" equals to "/news/". This causes a duplicate content which is considered bad for SEO and also is misleading because every visit of "/news/" with different language in the cookie return different content. I have done some fix for this that will be presented in the next post.

Conclusion: Thanks to all participants and to the guys at Django CMS - you do a really amazing job, I hope that you will like the features I proposed and that we will be able to see them in the next version. Comments and replies are welcomed as ever.

In the last few weeks I have been little busy(and suffering from lack of inspiration) so my blog lacks of new posts but I see that there are people visiting it(especially for the Django CMS stuff) so I am willing to start a "Post on Request" practice.

The idea is simple - I will collect post theme requests in the first three weeks(or 21 days) of every month and after a choose based on your votes( and my decision ) I`ll go out with a post on the selected theme by the end of the week. Please keep your question in the following areas - Django, Django CMS, Web Development. Question in other areas will be considered too, but may stand out of my knowledge area. You can place your request here or check the list and vote for another one or just comment this post.
I hope that you will find this initiative interesting and join it.

First of all please accept my apologies that I couldn't warn you for this drawback earlier but I was really busy in the last few weeks so let's skip directly to the problem.
If you remember in Extending Django CMS Page model – part II we added a method to the NavigationNode class that return an instance of the corresponding Page object. If we use it in the way show here:

The lambda function is executed every time when page_instance is called so this definetly increases the number of SQL queries made(+1 for every call of page_instance). Although this query is done using primary key and it is really fast this can bring you troubles. Especially if your hosting provider give you a limit of queries per time.
The good point is that it is not so big problem if you do it once or twice per page and it can be really useful. It all depends from how you use it. Also if you cache the output HTML you will skip the database overhead(but you have to be careful and make a mechanism that will invalidate the cache after page modifications)

(Almost) everything has its strong and weak sides, but using it carefully may bring you what you want. I really hope that someone will find this useful. If you do or you have found another weak/strong side do not hesitate to share your thoughts.

... or how to use the extended model in your templates and especially in the built-in navigation

The problem: As you can see in the previous post there is a very simple way to extend the page model with some custom fields without changing the core code. But how to use your custom fields inside your templates? If you have an instance of the Page model everything is fine. You can just access its properties and everything is fine. Unfortunately there is a problem if you try it inside a custom template used for show_menu template tag.

Speciality: I was really surprised when I tried to access my custom properties inside the mentioned above template and nothing happened. After some investigation I found that the elements in show_menu are not instances of the Page model but of NavigationNode. And even more surprised that NavigationNode does not contain instance of the Page model in its properties. So I was in need to extend the NavigationNode class.

Solution: First of all I decided to make it easier to access the custom properties I created before, so I added the following code to it:

For simplicity I have skipped the imports, but you can check them in the previous post
So now I have a "shortcut" for accessing the big_avatar and it is time to make the Page object available in the NavigationNode.

Line 2 defines a property("page_instance") that returns a Page object based on the primary key of the NavigationNode.id that equals to the corresponding Page primary key. Now you can use it in your custom navigation templates in the following way.

{%forchildinchildren%}{{child.page_instance.big_avatar}}{%endfor%}

Final words: I need to confess that I am really, really amazed how simply things can be done in Django and Django CMS. It is really awesome. I hope that you will find this post really helpful and useful. And as always do not be afraid to propose a better solutions or to ask for deeper explanation if something is not clear enough.

... or how to add some fields to the Page model in the admin without changing Django CMS core

The problem: Some times the Page model just lack of something you need. In my case this was "page avatars". Long story short - I needed an image/avatar for each page in my CMS. So what I have to do was to add a field to the Page model that will keep the info about the avatar path.

Speciality: Of course the simplest solution was just to edit the file(pagemodel.py) that contain the Page model. Unfortunately in the common case(and in my too) several different application resides on a single server and share the same Django CMS. So changing the core code is inconvenient because every change on it will affect all applications that rely on the same CMS core. So what? Copying the whole Django CMS files in my app and modifying them? This does not seems like a good solution too. Fortunately there is a simple way to do that and leave the core code unchanged.

Solution: First you need to create a new model that will hold the new fields you need and a foreign key to the Page model.

The last two lines(11 and 12) are used to force Django to reload the Page model admin.
Now you have your new field as an inline in the Page admin.

Final words: As you can see the solution is simple, fast and the core code is unaffected. There is an unique constraint on the page field in PageAvatars model so you will not be able to add more than one avatar per page.
If there is something unclear in the code or you have a better idea I am ready to hear it.